1. Field of the Invention
The subject matter of the invention is a sieving device with a vibratory supporting frame, with a vibration drive associated with and acting upon the supporting frame, and with a vibration frame held against the supporting frame via spring elements and spring-elastically coupled to the supporting frame, wherein the vibration frame can vibrate at least essentially freely in one direction of vibration (of tension waves), wherein the supporting frame and the vibration frame comprise transverse supports which are alternately arranged one behind the other in the direction of vibration and which, in particular, carry sieve bottom elements which can be tensioned and untensioned in the direction of vibration (of tension waves). Such a sieving device is, in particular, used for materials which are difficult to sieve, such as moist, sticky, caking materials and/or materials containing long fibers.
2. Description of Related Art
German Patent DE 35 03 125 C2 discloses a sieving device comprising a vibratory supporting frame and a vibration frame held to the supporting frame by spring elements so as to be able to vibrate. The transverse supports of the vibration frame extend through window-like apertures in side plates of the supporting frame towards the outside, where the transverse supports are connected to longitudinal supports of the vibration frame. Spring elements, preferably in the form of thrust-type rubber blocks, are arranged at several locations on each longitudinal support in a longitudinal direction, opposing each other in pairs on both sides of a longitudinal support. The thrust-type rubber blocks represent the only bearing arrangement of the vibration frame on the supporting frame, so that the vibration frame can carry out a vibration movement in relation to the supporting frame; said vibration movement being determined by the thrust-type rubber elements and being largely linear. To generate vibration, a vibration drive, which, in particular, is in the form of a withstand vibrations at high amplitude and high frequency even over extended periods. Accordingly, higher acceleration during tensioning of the sieve bottom elements and consequently increased or improved sieving performance, can be achieved. Greater acceleration is also beneficial for conveying the material to be sieved in the sieving direction. This is an additional reason for being able to reduce the inclination of the vibration frame or the direction of vibration in the sieving device according to the invention. When compared to the prior art, a reduction of the inclination of the vibration frame of 3xc2x0 to 5xc2x0 relative to the horizontal can be achieved. This results in a correspondingly considerably lower design height.
The provided torsion-bar-like spring elements are significantly less sensitive than thrust-type rubber blocks. In particular, the torsion-bar-like spring elements are virtually temperature-independent, thus providing for more universal application, without there being any danger of overheating. In addition, the service life of torsion-bar-like spring elements is significantly longer than those of thrust-type rubber blocks. Consequently, there is a reduction in the cost of operation and maintenance.
A simple and economic design of the sieving device is made possible in that the vibration frame is exclusively held by the torsion-bar-like spring elements on the supporting frame, so that no additional guiding elements for guiding the vibration frame are necessary.
Even though the main direction of effect of the vibration drive extends transversely as usual to the direction of vibration, in particular, to achieve good conveyance of the material to be sieved in the sieving direction, the spring elements can at least largely prevent interfering vibrations of the vibration frame transverse to the direction of vibration. In this respect, the torsion-bar-like spring elements are superior to the conventional thrust-type rubber elements.
A further aspect of the present invention provides for the sieving device to be operated or to be operable at an increased vibration frequency compared to the prior art, namely at least 850 vibrations per min. and, in particular, at approximately 890 vibrations per min. In this way in particular, an average speed of the vibration frame relative to the supporting frame of preferably at least 11 m/min and an average acceleration of preferably at least 2.2 m/s2 is achieved. In this way, a particularly strong vibration can be achieved which allows more effective sieving. Furthermore, better conveyance of the material to be sieved is achieved in the direction of sieving, so that the inclination of the vibration frame or the vibration can be significantly reduced, in particular, to 3xc2x0 to 5xc2x0 to the horizontal. Correspondingly, the required design height of the sieving device can be reduced.
Further details, characteristics, properties, advantages and aims of the present invention are described in the detailed description below and shown in more detail below by means of the drawing of the preferred embodiments.